Methods for determining mechanical specific energy for wellbore operations

ABSTRACT

A method for determining mechanical specific energy for a wellbore operation (e.g., drilling), the method including: measuring power input to machines used in a wellbore and producing a value for input power; calculating mechanical specific power for the operation based on the value for the input power; a computer-readable media for performing a step or steps of the method; and a computing unit for reading and performing the step or steps. This abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims, 37 C.F.R. 1.72( b ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to monitoring and controlling wellboreoperations; to monitoring and controlling wellbore drilling operationsin real time; and, in one particular aspect, to accomplishing thesethings by determining mechanical specific energy for an operation bytaking into account electrical or other energy input to one or moremachines used in such operations.

2. Description of the Related Art

The prior art discloses a wide variety of systems and methods formonitoring wellbore operations and for sensing and measuring parametersrelated to such operations, both downhole and at the surface. The priorart also discloses a wide variety of sensors, measurement apparatuses,devices, and equipment for sensing, measuring, recording, displaying,calculating, processing, and transmitting measured values foroperational parameters, including, but not limited to, weight on bit(WOB), rate of penetration (ROP), rotary speed, bit speed, top drivespeed, downhole motor speed, and torque on a drillstring or on a bit.

Many systems and methods have been proposed and implemented for usingsuch sensed and measured operational parameters to enhance, facilitate,and, in some cases, optimize operational performance and the performanceof apparatuses, devices and equipment involved in such operations;including, but not limited to, drilling operations. In 1965 R. Tealeproposed a model for analyzing and predicting drilling performance basedon a calculation of “mechanical specific energy” in an article entitled“The Concept Of Specific Energy In Rock Drilling” [Int'l J. Rock Mech.Mining Sci. (1965) 2, 5773]. Teale has a mathematical definition (“Tealedefinition”) of mechanical specific energy, which uses WOB (weight onbit), rig rotary speed in rpm's; torque at the bit; ROP (rate ofpenetration), and an area, i.e., wellbore (or bit) cross-sectional area.

In a 1992 research study, (see paper entitled “Quantifying CommonDrilling Problems With Mechanical Specific Energy And A Bit-SpecificCoefficient of Sliding Friction”, SPE 24584, 373388), R. C. Pessier etal developed an energy balance model for drilling under hydrostaticpressure using a comparison between full scale simulator tests and fielddata. As key indices of drilling performance, they employed mechanicalefficiency, Teale's mechanical specific energy parameter, and abit-specific coefficient of sliding friction for bit selection andanalysis. “Mechanical specific energy” was defined as work done per unitvolume of rock drilled and it was assumed that the minimum specificenergy required to drill is approximately equal to the compressivestrength of the rock being drilled. The mechanical efficiency ofdrilling was then estimated by comparing actual specific energy requiredto drill an interval with the minimum expected specific energy needed todrill that interval. Pessier et al analyzed values of various parameters(actual specific energy, minimum specific energy, energy efficiency, andbit specific coefficient of sliding friction) with respect to ROP underdifferent situations (e.g., different bits, different WOB's, differentRPM's, different hydraulics, and under atmospheric and hydrostaticpressure). It was concluded that mechanical specific energy, mechanicalefficiency, and bit specific coefficient of sliding friction providedgood indicators of drilling performance and could enhance theinterpretation of data for: the detection and correction of majordrilling problems; analysis and optimization of drilling practices; bitselection; failure analysis; evaluation of new drilling technologies andtools; realtime monitoring and controlling of the drilling process;analysis of MWD (measurement while drilling) data; and further systemdevelopments.

In a 2002 paper, Waughman et al reported on a system and method foroptimizing the bit replacement decision [“Real Time Specific EnergyMonitoring Reveals Drilling Inefficiency and Enhances the Understandingof When to Pull Worn PDC Bits”, IADC/SPE 74520, 2002, 114]. The systeminvolved measuring the mechanical energy input at the drill rig floor,calculating the drilling specific energy, checking current formationtype via realtime downhole gamma ray readings, comparing the specificenergy with the benchmark new bit specific energy, and then using thesevalues to assess the bit's state. Success of the system was reported forsynthetic based mud systems where bit balling does not mask bit dullcondition. The process worked in water-base drilling fluids that hadreplaced earlier synthetic muds because both balled-new bits and dullbits exhibit similar levels of inefficiency.

In general, certain prior art systems and methods use calculations ofmechanical specific energy based on sensed and measured values ofdrilling parameters. Data is often obtained from locations at the bit.For example, torque and rotational speed (rpm's) can be measured atvarious locations, e.g. downhole or at the surface, and the measurement,from whichever location, is then used.

U.S. Pat. No. 7,243,735, co-owned with the present invention, disclosesmethods for wellbore operations with a wellbore system, the methodsincluding: acquiring with sensor systems data corresponding to aplurality of parameters, the data indicative of values for eachparameter of the plurality of parameters, each parameter correspondingto part of the wellbore system; based on said data, calculating amechanical specific energy value for each of a plurality of mechanicalspecific energies each related to a mechanical specific energy for apart of the wellbore system; and monitoring the value of each of themechanical specific energies, in one aspect, in real time. Systems andmethods are disclosed for determining localized differentiatedmechanical specific energy parameters: surface mechanical specificenergy; drillstring mechanical specific energy; and bit (or mill orother apparatus) mechanical specific energy. The patent also discloses amethod for a wellbore operation with a wellbore system, the methodincluding: acquiring with sensor systems data corresponding to aplurality of parameters, the data indicative of values for eachparameter of the plurality of parameters, each parameter correspondingto part of the wellbore system; based on the data, calculating amechanical specific energy value for each of a plurality of mechanicalspecific energies each related to a mechanical specific energy for apart of the wellbore system; monitoring the value of each of themechanical specific energies; and wherein the wellbore operation is anoperation with a rotating bit and values for the mechanical specificenergies are calculated according to the equation for Teale's definitionof mechanical specific energy.

In known methods for calculating mechanical specific energy, only themechanical components are been taken into account. Certain known methodsfor calculating mechanical specific energy require a relatively largeamount of data and, sometimes, calibration and re-calibration of weighton bit, bit RPM, bit torque and rate of penetration. Actual bitrotational speeds and torques can frequently be difficult to determineprecisely and accurately. This can occur when using a downhole motor orturbine to rotate a bit. Certain known methods do not take into accountthe actual energy used on a rig to drill a wellbore.

BRIEF SUMMARY OF THE INVENTION

The present invention discloses, in certain aspects, methods fordetermining mechanical specific energy for a wellbore operation, e.g., adrilling operation, milling, reaming, etc., which takes into account theenergy (power) input to machines which are involved in the operation,e.g. for rotation of a drill bit, mill, or reamer, etc. In certainaspects, this includes energy input to a top drive, or a rotary table,and/or mud pumps.

The present invention discloses, in certain embodiments, methods fordetermining the mechanical specific energy (in one aspect, in real time)for a wellbore operation without using values for certain measuredparameters, e.g., drilling or milling or reaming parameters, but ratherwhich use measurements of values of energy (e.g. electrical orhydraulic) input into equipment involved in an operation. Often indrilling or other operations utilizing downhole mud motors, there are nosensors, e.g. for bit torque or RPM. Further, even in some existingconventional operations without downhole motors, surface measurements,e.g. of speed and torque, can vary considerably from the values at thebit.

The present invention, in certain aspects, discloses a method fordetermining mechanical specific energy for a wellbore operation (e.g.drilling, milling, reaming), the method including: measuring power inputto machines used in a wellbore operation and producing a value for inputpower, and calculating mechanical specific energy for the operationbased on the value for the input power. The present invention alsodiscloses a computer-readable media having computer executableinstructions for a method according to the present invention, thecomputer-executable instructions performing a step or steps of themethod.

The present invention, in certain aspects, discloses a computing unitconfigured to read and perform the computer-executable instructions oncomputer-readable media.

The present invention discloses, in certain aspects, a method whereinMechanical Specific Energy, MSE, is calculated according to the equation

MSE=(r)(Power)/(D ²)(ROP)

in which “r” is a constant for converting units of power to units ofMSE; “Power” is energy input to the machines; “D” is diameter of a bitused for the drilling; and “ROP” is rate of penetration of the bit intoa formation being drilled. This calculating can be done in real time.

In addition to specific objects stated herein for at least certainpreferred embodiments of the invention (but not necessarily for allembodiments of the present invention), other objects and purposes willbe readily apparent to one of skill in this art who has the benefit ofthis invention's teachings and disclosures. It is, therefore, an objectof at least certain preferred embodiments of the present invention toprovide new, unique, useful, and non-obvious systems and methods oftheir use all of which are not anticipated by, rendered obvious by,suggested by, or even implied by any of the prior art, either alone orin any possible legal combination.

Accordingly, the present invention includes features and advantageswhich are believed to enable it to advance wellbore operationsmonitoring and control technology. Characteristics and advantages of thepresent invention described above and additional features and benefitswill be readily apparent to those skilled in the art upon considerationof the following description of preferred embodiments and referring tothe accompanying drawings.

Certain embodiments of this invention are not limited to any particularindividual feature disclosed here, but include combinations of themdistinguished from the prior art in their structures, functions, and/orresults achieved. Features of the invention have been broadly describedso that the detailed descriptions of embodiments preferred at the timeof filing for this patent that follow may be better understood, and inorder that the contributions of this invention to the arts may be betterappreciated. There are, of course, additional aspects of the inventiondescribed below and which may be included in the subject matter of theclaims to this invention. Those skilled in the art who have the benefitof this invention, its teachings, and suggestions will appreciate thatthe conceptions of this disclosure may be used as a creative basis fordesigning other structures, methods and systems for carrying out andpracticing the present invention. The claims of this invention are to beread to include any legally equivalent devices or methods which do notdepart from the spirit and scope of the present invention.

What follows are some of, but not all, the objects of this invention. Inaddition to the specific objects stated below for at least certainembodiments of the invention, other objects and purposes will be readilyapparent to one of skill in this art who has the benefit of thisinvention's teachings and disclosures. It is, therefore, an object of atleast certain embodiments of the present invention to provide theembodiments and aspects listed above and:

New, useful, unique, efficient, non-obvious methods for accuratelydetermining the mechanical specific energy for a wellbore operation,e.g. a drilling, milling, or reaming operation; and

Such methods which employ values for electrical energy supplied tomachines involved in the operation, e.g. in rotating a drill bit todrill a wellbore, a mill, or a reamer;

Such methods which do not use a variety of directly measured parametersto calculate mechanical specific energy, e.g. but not limited to,drilling parameters; and

Such methods that take into account the energy supplied to mud pumpsused in pumping drilling fluid for a drilling operation and/or fordriving a downhole motor that rotates a drill bit.

The present invention recognizes and addresses the problems and needs inthis area and provides a solution to those problems and a satisfactorymeeting of those needs in its various possible embodiments andequivalents thereof. To one of skill in this art who has the benefits ofthis invention's realizations, teachings, disclosures, and suggestions,various purposes and advantages will be appreciated from the followingdescription of preferred embodiments, given for the purpose ofdisclosure, when taken in conjunction with the accompanying drawings.The detail in these descriptions is not intended to thwart this patent'sobject to claim this invention no matter how others may later attempt todisguise it by variations in form, changes, or additions of furtherimprovements.

The Abstract that is part hereof is to enable the U.S. Patent andTrademark Office and the public generally, and scientists, engineers,researchers, and practitioners in the art who are not familiar withpatent terms or legal terms of phraseology to determine quickly, from acursory inspection or review the nature and general area of thedisclosure of this invention. The Abstract is neither intended to definethe invention, which is done by the claims, nor is it intended to belimiting of the scope of the invention or of the claims in any way.

It will be understood that the various embodiments of the presentinvention may include one, some, or all of the disclosed, described,and/or enumerated improvements and/or technical advantages and/orelements in claims to this invention.

Certain aspects, certain embodiments, and certain preferable features ofthe invention are set out herein. Any combination of aspects or featuresshown in any aspect or embodiment can be used except where such aspectsor features are mutually exclusive.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A more particular description of embodiments of the invention brieflysummarized above may be had by references to the embodiments which areshown in the drawings which form a part of this specification. Thesedrawings illustrate embodiments preferred at the time of filing for thispatent and are not to be used to improperly limit the scope of theinvention which may have other equally effective or legally equivalentembodiments.

FIG. 1 is a schematic view of a system which can employ methodsaccording to the present invention.

FIG. 2 is a schematic view of steps of a method according to the presentinvention.

FIG. 3 is a graphic illustration of methods according to the presentinvention.

Certain embodiments of the invention are shown in the above-identifiedfigures and described in detail below. Various aspects and features ofembodiments of the invention are described below and some are set out inthe dependent claims. Any combination of aspects and/or featuresdescribed below or shown in the dependent claims can be used exceptwhere such aspects and/or features are mutually exclusive. It should beunderstood that the appended drawings and description herein are ofcertain embodiments and are not intended to limit the invention or theappended claims. On the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the invention as defined by the appended claims. In showingand describing these embodiments, like or identical reference numeralsare used to identify common or similar elements. The figures are notnecessarily to scale and certain features and certain views of thefigures may be shown exaggerated in scale or in schematic in theinterest of clarity and conciseness.

As used herein and throughout all the various portions (and headings) ofthis patent, the terms “invention”, “present invention” and variationsthereof mean one or more embodiments, and are not intended to mean theclaimed invention of any particular appended claim(s) or all of theappended claims. Accordingly, the subject or topic of each suchreference is not automatically or necessarily part of, or required by,any particular claim(s) merely because of such reference. So long asthey are not mutually exclusive or contradictory any aspect or featureor combination of aspects or features of any embodiment disclosed hereinmay be used in any other embodiment disclosed herein.

DETAILED DESCRIPTION OF THE INVENTION

In one particular embodiment of a system and method according to thepresent invention, as shown in FIG. 1, a system 10 has a drilling rig 11depicted schematically as a land rig, but other rigs (e.g., offshorerigs and platforms, jack-up rigs, semi-submersibles, drill ships, andthe like) are within the scope of the present invention. In conjunctionwith an operator interface, e.g. an interface I, a control system 14controls operations of the rig. The rig 11 includes a derrick 13 that issupported on the ground above a rig floor 15. The rig 11 includeslifting apparatus, a crown block 17 mounted to derrick 13 and atraveling block 19 interconnected by a cable 21 that is driven by adrawworks 23 (with an electrically powered motor or motors 23 m) tocontrol the upward and downward movement of the traveling block 19.Traveling block 19 carries a hook 25 from which is suspended a top drivesystem 27 which includes a variable frequency drive controller 26, amotor (or motors) 24, electrically powered, and a drive shaft 29. Apower swivel may be used instead of a top drive. The top drive system 27rotates a drillstring 31 to which the drive shaft 29 is connected in awellbore 33. The top drive system 27 can be operated to rotate thedrillstring 31 in either direction. A rotary system 60 has a motor 60 mand a rotary table and kelly used to rotate the drillstring. In oneaspect, the drillstring 31 is coupled to the top drive system 27 throughan instrumented sub 39 which includes sensors that provide drillingparameter information.

The drillstring 31 may be any typical drillstring and, in one aspect,includes a plurality of interconnected sections of drill pipe 35 abottom hole assembly (BHA) 37, which can include stabilizers, drillcollars, and/or an apparatus or device, in one aspect, a suite ofmeasurement while drilling (MWD) instruments including a steering tool51 to provide bit face angle information. Optionally a bent sub 41 isused with a downhole or mud motor 42 and a rotatable member 56 which, inone aspect, is a bit, connected to the BHA 37. The face angle of the bit56 can be controlled in azimuth and pitch during drilling. Optionally,the rotatable member 56 is replaced with a mill, reamer, or reaming bit.

Drilling fluid is delivered to the drillstring 31 by mud pumps 43 whichhave an electrically-powered motor or motors 43 m through a mud hose 45.The drillstring 31 is rotated within bore hole 33 by the top drivesystem 27 (and/or by the rotary system 60; and/or by the mud motor 42).During sliding drilling, the drillstring 31 is held in place by topdrive system 27 while the bit 56 is rotated by the mud motor 42, whichis supplied with drilling fluid by the mud pumps 43. The driller canoperate the top drive system 27 to change the face angle of the bit 56.The cuttings produced as the bit drills into the earth are carried outof bore hole 33 by drilling mud supplied by the mud pumps 43.Optionally, machines are hydraulically powered instead of electricallypowered.

A rig power system 70 is the overall power system powered as shown bythree individual engine generator sets 72 a, 72 b, 72 c (sometimescalled prime movers) or may be supplied energy from an alternativesource as, for example, a utility distribution on a land rig or a feedfrom a large power generation unit for a very large offshore fixedinstallation. Regardless of the primary power source, individual powercontrol is provided to equipment on the drilling rig needing such; e.g.each of the items 23, 27, 43 and/or 60, optionally, has its own singleboard computer 23 c, 27 c, 43 c and 60 c respectively. The single boardcomputers 23 c, 27 c, 43 c and 60 c each have programmable mediaprogrammed so that each separate computer can control its particulartool or system. The computer is programmed to perform desiredcalculations. Each single board computer can control its respective toolor system. Optionally, a main control system 14 can control all rigfunctions and is in communication with each single board computer. Inone aspect this is classified as auxiliary loads 65 which are suppliedpower from a transformer 71, e.g. such things as lighting, centrifugalpumps, and hotel loads. In addition to these are drilling task specificloads, as, for example, the drawworks 23 whose motor is powered by aconverter 73 b. Other loads are the top drive 27 or the rotary table 60whose motors 27 m and 60 m, respectively, are powered by a converter 73a. Additionally mud pumping loads consist of from one to three or moremud pumps 43 each with at least one motor 43 m, powered by a converter73 c.

In one aspect power being used by either of the rotators (either therotary table 60 or the top drive 27 and/or by the mud pumps) ismonitored instantaneously. Power monitor devices 27 p, 60 p, and 43 pmeasure the power being consumed by the top drive 27, the rotary table60, or the mud pumps 43, respectively. The system 14 may include adisplay D for displaying calculated MSE in real time.

FIG. 2 shows steps in a method according to the present invention fordetermining mechanical specific energy, MSE, expressed as energy inputto a system per volume of rock drilled (or of item milled or of wellborereamed). Electrical energy input into drilling equipment is measured(“MEASUREMENT ENERGY INPUTS”); e.g., for the motors of a rotary, topdrive, mud pumps and/or a drawworks. The equipment, in one aspect,includes electric motor(s) and the mud pumps. According to the presentinvention, measured energy inputs can include energy in eitherelectrical or hydraulic form; e.g. for hydraulically driven machines,e.g. hydraulically powered top drives, the fluid volume and pressure.

The energy input to the motors is determined based on the electricalpower sensed and measured by power monitor devices 43 p, 27 p, and 60 p.

Voltages and the amperages can be measured using, e.g. cabling orelectrical bus bars to the electric motors, either AC or DC.

In some embodiments, the top drive or rotary table might behydraulically powered, in which case the present invention woulddetermine the power from the conventional means of multiplying flow rateand volume with appropriate scaling.

Energy input is expressed in typical energy units, e.g. in kilowatts.The rate of penetration is measured by any suitable known method andapparatus, e.g. by encoder or other means (“MEASUREMENT ROP”) andexpressed in feet per hour. The bit diameter (“BIT DIAMETER VALUE”) isexpressed in inches.

A computer or similar apparatus (“CALCULATOR”) receives the variousmeasurements, processes them and calculates the mechanical specificenergy (“MSE”).

For a typical top drive motor, mud pump motor, or rotary motor, theproduct of the voltage and amperage from their respective generators isproportional to the developed horsepower. The product of the voltagetimes the amperage is a number of kilowatts.

Similarly, the product of the applied voltage times the amperage for themotors of the mud pumps is a number of kilo watts. The mud pumps providethe motive fluid for a downhole mud motor with respect to which theapplied voltage is proportional to the resulting bit rotational speed inrpm's and the change in amperage of the mud pump motors is proportionalto the applied torque of the bit into the formation, and this isproportional to the torque of the rotating bit.

Once the energy inputs and other values are determined, the calculatorcalculates MSE.

In one situation, drilling conventionally with a surface rotator, i.e. arotary table or top drive (either one or the other only, henceforthreferred to as “rt/td”) and with no downhole motor imparting rotation tothe bit. Then with direct measurement of the top drive or rotary tablepower measured in KW, the formula for MSE is:

MSE_(conventional)=(3,380. 7*KW_(rt/td))/(D ²*ROP)

In another situation, drilling is done with a downhole mud motor and“sliding”, that is, the downhole mud motor is imparting all of therotational torque to the bit and the rt/td is not spinning. Then, withdirect measurement of the mud pump KW, both on-bottom and off-bottom,with the on-bottom measurement having the off-bottom subtracted from itto form a ΔPumpKW, the formulation for MSE then is:

Δ_(PumpKW)=KW_(on) _(—) _(bottom)−KW_(off) _(—) _(bottom)

MSE_(conventional) _(—) _(DH)=(3,380.7*Δ_(PumpKW))/(D ²*ROP)

“KWoff_bottom” is the KW expended by the drilling fluid in rotating thedownhole mud motor with the bit not touching, or engaged with, thebottom of the formation. “KWoff_bottom” is the KW expended by thedrilling fluid in rotating the downhole mud motor with the bit engagedwith the formation.

In another situation, drilling is done with both a downhole mud motorand a surface rotator (rt/td) simultaneously. Then, with directmeasurement of both rotational and incremental hydraulic power used bythe downhole mud motor, the formula for MSE is:

MSE_(combined)=(3,380.7*(KW_(rt/td)+Δ_(PumpKW)))/(D ²*ROP)

In another situation the hydraulic power imparted to the formation bythe mud pumps acting with the bit jets is taken into account. However an“MSE TOTAL” or “figure of merit” corresponding to an intrinsicdefinition of MSE can be of value and is determined from the measuredKW's and defined as:

MSE_(Total)=(3,380.7*(KW_(rt/td)+KW_(on) _(—) _(bottom)))/(D ²*ROP)

This MSE TOTAL takes into account the power imparted to the formation bythe action of the mud pumps pumping mud through the jets. Thus, usingvoltage and amperage measurements, MSE is determined for a drillingoperation. In certain aspects, using the same measurements of electricalenergy inputs for the mud pump motors, MSE is determined for adownhole-motor drilling operation. When two or three of these drillingmodes are employed together, a combined MSE taking into account energyinput for each mode is determined. All of these determinations can bedone without taking into account and without the need for measuring thespeed of a rotary table, the speed of a top drive shaft, and the actualtorque applied to a bit. The last of these methods according to thepresent invention also take into account the energy input associatedwith energy expended through the downhole motor's fluid jets. Certainknown methods do not take into account the hydraulic horsepower of mudflow across a drill bit's jets; but, since certain methods of thepresent invention are cognizant of the energy supplied to the mud pumps,this energy expended in the drilling operation can, according to thepresent invention, be considered.

FIG. 3 presents a summary of the methods according to the presentinvention for the various situations described above. Optionally, themethods described are used for a milling operation, a reaming operation,or for similar operations.

The present invention, therefore provides, in at least certainembodiments, a method for determining mechanical specific energy for awellbore operation, the method including measuring power input tomachines used in the operation, e.g a wellbore drilling operation andproducing a value for input power, calculating mechanical specificenergy for the operation based on the value for the input power. Such amethod according to the present invention may have one or some (in anypossible combination) of the following: wherein the wellbore operationis a drilling operation, wherein the power input is electrical power andthe value for input power is a value for electrical power; wherein thepower input is hydraulic power and the value for input power is a valuefor hydraulic power; wherein the machines include a rotator for rotatingtubulars used in the wellbore operation; wherein the rotator is at leastone of rotary table system, top drive system, and mud motor system;wherein measuring the power input includes measuring power for a mudpump system and power for at least one rotator for rotating tubularsused in the wellbore operation; wherein the at least one rotator is allrotators used for rotating tubulars used in the wellbore operation;wherein the wellbore operation is a wellbore drilling operation usingonly either a rotary table system or a top drive system and MechanicalSpecific Energy, MSE, is calculated according to the equation,

MSE_(conventional)=(3,380.7*KW_(rt/td))/(D ²*ROP)

in which “KW” is input power measured in kilowatts; “D” is bit diameterarea for the drill bit used; and “ROP” is rate of penetration of thedrill bit through the formation; wherein the wellbore operation is adrilling operation using a downhole mud motor to rotate a drill bit todrill a wellbore and Mechanical Specific Energy, MSE, is calculatedaccording to the equation,

Δ_(PumpKW)=KW_(on) _(—) _(bottom)−KW_(off) _(—) _(bottom)

MSE_(conventional) _(—) _(DH)=(3,380.7*Δ_(PumpKW))/(D ²*ROP)

in which “KW” is input power measured in kilowatts; “D” is bit diameterarea for the drill bit used; and “ROP” is rate of penetration of thedrill bit through the formation, and “ΔPUMPKW” is the difference betweenkilowatts input to a mud pump system used in the wellbore drillingoperation with the bit on-bottom (“KW on bottom”), and off-bottom of thewellbore (“KW off bottom); wherein the wellbore operation is a drillingoperation using a rotator for rotating tubulars and a downhole mud motorto rotate a drill bit, and Mechanical Specific Energy, MSE, iscalculated according to the equation,

MSE_(combined)=(3,380.7*(KW_(rt/td)+Δ_(PumpKW)))/(D ²*ROP)

in which “KW” is input power measured in kilowatts; “D” is bit diameterarea for the drill bit used; and “ROP” is rate of penetration of thedrill bit through the formation, and “ΔPUMPKW” is the difference betweenkilowatts input to a mud pump system used in the wellbore drillingoperation with the bit on-bottom (“KW on bottom”), and off-bottom of thewellbore (“KW off_bottom); wherein the wellbore operation is a drillingoperation and the wellbore is being drilled with a downhole mud motorusing an hydraulically powered mud pump system which inputs power to aformation being drilled via mud pumped through a drill bit being used todrill the wellbore, and Mechanical Specific Energy, MSE, is calculatedaccording to the equation:

MSE_(Total)=(3,380.7*(KW_(rt/td)+KW_(on) _(—) _(bottom)))/(D ²*ROP)

in which “KW” is input power measured in kilowatts; “D” is bit diameterarea for the drill bit used; and “ROP” is rate of penetration of thedrill bit through the formation, and KW on bottom is power input to thedownhole mud motor; supply power to the machines with a rig powersystem; wherein the wellbore operation is a drilling operation andMechanical Specific Energy, MSE, is calculated according to theequation:

MSE=(r)(Power)/(D ²)(ROP)

in which “r” is a constant for converting units of power to units ofMSE, Power is energy input to the machines used in the operation, “D” isdiameter of a bit used for the drilling; and ROP is rate of penetrationof the bit into a formation being drilled; wherein said calculating isdone in real time; controlling the measuring and the calculating with acontrol system; and/or displaying calculated MSE in real time.

The present invention therefore provides, in at least certainembodiments, a computer-readable media having computer executableinstructions for a method according to the present invention, thecomputer-executable instructions performing a step or steps of themethod.

The present invention therefore provides, in at least certainembodiments, a computing unit configured to read and perform thecomputer-executable instructions on computer-readable media according tothe present invention.

The present invention therefore provides, in at least certainembodiments, a method wherein the wellbore operation is a wellboredrilling operation and Mechanical Specific Energy, MSE, is calculatedaccording to the equation:

MSE=(r)(Power)/(D ²)(ROP)

in which “r” is a constant for converting units of power to units ofMSE; Power is energy input to machines for a wellbore operation; “D” isdiameter of a bit used for the drilling; operation (e.g. drilling); andROP is rate of penetration of the bit into a formation being drilled (orof a mill into an item being milled or of a wellbore being reamed).

In conclusion, therefore, it is seen that the present invention and theembodiments disclosed herein and those covered by the appended claimsare well adapted to carry out the objectives and obtain the ends setforth. Certain changes can be made in the subject matter withoutdeparting from the spirit and the scope of this invention. It isrealized that changes are possible within the scope of this inventionand it is further intended that each element or step recited in any ofthe following claims is to be understood as referring to the stepliterally and/or to all equivalent elements or steps. The followingclaims are intended to cover the invention as broadly as legallypossible in whatever form it may be utilized. The invention claimedherein is new and novel in accordance with 35 U.S.C. §102 and satisfiesthe conditions for patentability in §102. The invention claimed hereinis not obvious in accordance with 35 U.S.C. §103 and satisfies theconditions for patentability in §103. This specification and the claimsthat follow are in accordance with the requirements of 35 U.S.C. §112.The inventors may rely on the Doctrine of Equivalents to determine andassess the scope of their invention and of the claims that follow asthey may pertain to apparatus and/or methods not materially departingfrom, but outside of, the literal scope of the invention as set forth inthe following claims. All patents and applications identified herein areincorporated fully herein for all purposes. It is the express intentionof the applicant not to invoke 35 U.S.C. §112, paragraph 6 for anylimitations of any of the claims herein, except for those in which theclaim expressly uses the words ‘means for’ together with an associatedfunction. In this patent document, the word “comprising” is used in itsnon-limiting sense to mean that items following the word are included,but items not specifically mentioned are not excluded. A reference to anelement by the indefinite article “a” does not exclude the possibilitythat more than one of the element is present, unless the context clearlyrequires that there be one and only one of the elements.

Whereas the present invention has been described in particular relationto the drawings attached hereto, it should be understood that other andfurther modifications apart from those shown or suggested herein, may bemade within the scope and spirit of the present invention.

1. A method for determining mechanical specific energy for a wellboreoperation, the method comprising: measuring power input to machines usedin a wellbore operation and producing a value for input power,calculating mechanical specific energy for the operation based on thevalue for the input power.
 2. The method of claim 1 wherein the powerinput is electrical power and the value for input power is a value forelectrical power.
 3. The method of claim 1 wherein the power input ishydraulic power and the value for input power is a value for hydraulicpower.
 4. The method of claim 1 wherein the machines include a rotatorfor rotating tubulars used in the wellbore operation.
 5. The method ofclaim 4 wherein the rotator is at least one of rotary table system, topdrive system, and mud motor system.
 6. The method of claim 1 whereinmeasuring the power input includes measuring power for a mud pump systemand power for at least one rotator for rotating tubulars used in thewellbore operation.
 7. The method of claim 6 wherein the at least onerotator is all rotators used for rotating tubulars used in the wellboreoperation.
 8. The method of claim 1 wherein the wellbore operation is awellbore drilling operation using only either a rotary table system or atop drive system and Mechanical Specific Energy, MSE, is calculatedaccording to the equation:MSE_(conventional)=(3,380.7*KW_(rt/td))/(D ²*ROP) in which “KW” is inputpower measured in kilowatts; “D” is bit diameter area for the drill bitused; and “ROP” is rate of penetration of the drill bit through theformation.
 9. The method of claim 1 wherein the wellbore operation is awellbore drilling operation using a downhole mud motor to rotate a drillbit to drill a wellbore and Mechanical Specific Energy, MSE, iscalculated according to the equations:Δ_(PumpKW)=KW_(on) _(—) _(bottom)−KW_(off) _(—) _(bottom)MSE_(conventional) _(—) _(DH)=(3,380.7*Δ_(PumpKW))/(D ²*ROP) in which“KW” is input power measured in kilowatts; “D” is bit diameter area forthe drill bit used; and “ROP” is rate of penetration of the drill bitthrough the formation, and “ΔPUMPKW” is the difference between kilowattsinput to a mud pump system used in the wellbore drilling operation withthe bit on-bottom (“KW on_bottom”), and off-bottom of the wellbore (“KWoff_bottom).
 10. The method of claim 1 wherein the wellbore operation isa wellbore drilling operation using a rotator for rotating tubulars anda downhole mud motor to rotate a drill bit, and Mechanical SpecificEnergy, MSE, is calculated according to the equation:MSE_(combined)=(3,380.7*(KW_(rt/td)+Δ_(PumpKW)))/(D ²*ROP) in which “KW”is input power measured in kilowatts; “D” is bit diameter area for thedrill bit used; and “ROP” is rate of penetration of the drill bitthrough the formation, and “ΔPUMPKW” is the difference between kilowattsinput to a mud pump system used in the wellbore drilling operation withthe bit on-bottom (“KW on_bottom”), and off-bottom of the wellbore (“KWoff_bottom).
 11. The method of claim 1 wherein the wellbore operation isa wellbore drilling operation and a wellbore is being drilled with adownhole mud motor using an hydraulically powered mud pump system whichinputs power to a formation being drilled via mud pumped through a drillbit being used to drill the wellbore, and Mechanical Specific Energy,MSE, is calculated according to the equation:MSE_(Total)=(3,380.7*(KW_(rt/td)+KW_(on) _(—) _(bottom)))/(D ²*ROP) inwhich “KW” is input power measured in kilowatts; “D” is bit diameterarea for the drill bit used; and “ROP” is rate of penetration of thedrill bit through the formation, and KW on bottom is power input to thedownhole mud motor.
 12. The method of claim 1 further comprising supplypower to the machines with a rig power system.
 13. The method of claim 1wherein the wellbore operation is a drilling operation and MechanicalSpecific Energy, MSE, is calculated according to the equation,MSE=(r)(Power)/(D ²)(ROP) in which: r is a constant for converting unitsof power to units of MSE; Power is energy input to the machines used inthe operation; D is diameter of a bit used for the drilling; and ROP israte of penetration of the bit into a formation being drilled.
 14. Themethod of claim 1 wherein said calculating is done in real time.
 15. Themethod of claim 1 further comprising controlling the measuring and thecalculating with a control system.
 16. The method of claim 15 furthercomprising displaying calculated MSE in real time.
 17. Acomputer-readable media having computer executable instructions for amethod as in claim 1, the method including measuring power input tomachines used in drilling a wellbore and producing a value for inputpower, the computer-executable instructions performing the followingstep: calculating mechanical specific energy for the drilling based on ameasured value for the input power.
 18. A computing unit configured toread and perform the computer-executable instructions oncomputer-readable media as recited in claim
 17. 19. The method of claim1 wherein the wellbore operation is a wellbore drilling operation andMechanical Specific Energy, MSE, is calculated according to theequation,MSE=(r)(Power)/(D ²)(ROP) in which: r is a constant for converting unitsof power to units of MSE; Power is energy input to machines used in theoperation; D is diameter of a bit used for the drilling; and ROP is rateof penetration of the bit into a formation being drilled.
 20. The methodof claim 1 wherein said calculating is done in real time.